This invention provides a self-powered freight-carrying vehicle. The unit is intended to replace the usual combination of a farm tractor and a flat-bed trailer for certain operations. These two are normally coupled together with a standard hitch that provides relative articulation about a vertical axis. The tractor is a separate controllable vehicle on its own, and designed to accommodate a wide variety of other uses. Maneuverability of the combination of the tractor and the trailer in close quarters is quite limited. In agricultural operations in orchards, this factor is critical. Trees are closely planted, and must not be subject to damage by moving equipment. It should also be noted that a standard farm tractor is a substantial investment, and represents a capacity to perform functions that often are needed at the same time that the freight-carrying operation is underway. Where a considerable amount of the freight-carrying function is needed, the usual tractor can be freed for other work by a much simpler machine at a correspondingly lower cost.